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  Method and apparatus for analyzing thermo-graphic images to detect defects in thermally sealed packagingUSPTO Application #: 20070237201Title: Method and apparatus for analyzing thermo-graphic images to detect defects in thermally sealed packaging Abstract: A method of monitoring and detecting thermal sealing defects includes capturing a thermal image of a thermal seal, obtaining a reference thermal image corresponding to an acceptable thermal seal, converting the captured thermal image to a first sequenced set of pixel values, converting the reference thermal image to a second sequenced set of pixel values, defining a plurality of regions such that each region includes a plurality of sequence numbers such that each sequence number is a sequence number of a pixel value in the first sequenced set, generating a sequenced set of differential values such that each differential value is associated with the first ordered set of pixel values and with the second ordered set of pixel values, and analyzing the sequenced set of differential values. (end of abstract)
Agent: Marshall, Gerstein & Borun LLP - Chicago, IL, US Inventor: Steven Ignatowicz USPTO Applicaton #: 20070237201 - Class: 374 7 (USPTO) The Patent Description & Claims data below is from USPTO Patent Application 20070237201. Brief Patent Description - Full Patent Description - Patent Application Claims
CROSS-REFERENCE TO RELATED APPLICATIONS [0001]This application claims benefit of the following United States Provisional Applications: Ser. No. 60/789,974, entitled "An Improved Method and Apparatus for Analyzing Thermographic Images to Detect Defects in Thermally Sealed Packaging" filed Apr. 6, 2006 (attorney docket no. 29123/40154B), the disclosure of which is hereby expressly incorporated herein by reference. FIELD OF THE DISCLOSURE [0002]The present disclosure is generally directed to method and apparatus for detecting defects in plastic sealing and, more particularly, a method and apparatus for detecting defects in plastic sealing using an infrared imaging system. BACKGROUND OF THE DISCLOSURE [0003]Thousands of different products are packaged in some kind of plastic container. The food industry uses them for such items as frozen pizza, frozen vegetables and fountain soda. One example is ajar of nuts where a metalized paper cover is secured to the jar by induction heating of the lid. The medical industry uses plastic bags for IV solutions and blood among others. For example, containers are the sealed by pressing a top and bottom of the container together with heater bars. In some cases a failed seal may affect the shelf life of the product or allow contaminants to enter. In another case, such as holding laundry detergent tablets, a failed seal is just a nuisance for the user. In any case, a failed seal ultimately reflects on the quality image of the supplier which may lead to a decline in future sales. [0004]For some applications product is being sealed inside, while for others the product is the specialty plastic bag. Whether sealing in the final product or just making seals to create a bag, the process is similar. The product is indexed along the process line where it enters a heating press. The press is clamped on the areas to be sealed and then heat is applied until the plastic components are fused together. Heat is removed to start the cooling cycle before the press is released. The cycle repeats with the next part being indexed into position. Manufacturers run the cycle as quickly as possible to maximize production yield, but unfortunately the seal defects increase as the cycle speed is increased. [0005]A thermal imaging system may function both as a tool to increase the cycle speed and also as an automatic fault detection system. Such systems may be optimized by programming the system to look past the surface of the object they are measuring, and concentrating on the actual seal that is buried beneath the surface. In doing so, a sublet defect will be more readily detected. BRIEF DESCRIPTION OF THE DRAWINGS [0006]Objects, features, and advantages of the present device will become apparent upon reading the following description in conjunction with the drawing figures, in which: [0007]FIG. 1 is an isometric view of one example of an infrared imaging system used in detecting defects in plastic seals constructed according to one embodiment of the disclosure; [0008]FIG. 2 is a block diagram of the infrared imaging system of FIG. 1. [0009]FIG. 3 is an example of a partial thermal image of a plurality of seals as obtained from the infrared imaging system of FIG. 1; [0010]FIG. 4 is an example plot of image intensity levels of a reference image; [0011]FIG. 5 is an example plot of image intensity levels of an test image; [0012]FIG. 6 is a plot of the difference in intensity levels between the reference image of FIG. 4 and the test image of FIG. 5, utilizing a typical image matching scheme; [0013]FIG. 7 is a plot of the difference in intensity levels between the reference image of FIG. 4 and the test image of FIG. 5, according to the image matching scheme disclosed herein; [0014]FIG. 8 is a flowchart of one exemplary operation of monitoring and detecting a defect in a thermal seal using the infrared imaging system of FIG. 1; and [0015]FIG. 9 is a flow diagram illustrating the image matching scheme utilized in obtaining the plot of FIG. 7. [0016]While the method and device described herein are susceptible to various modifications and alternative constructions, certain illustrative embodiments thereof have been shown in the drawings and will be described below in detail. It should be understood, however, that there is no intention to limit the invention to the specific forms disclosed, but on the contrary, the intention is to cover all modifications, alternative constructions, and equivalents falling within the spirit and scope of the disclosure. DETAILED DESCRIPTION OF THE DISCLOSURE [0017]Referring now to the drawings and with specific reference to FIG. 1, an infrared imaging system constructed in accordance with the teachings of the disclosure is generally depicted by reference numeral 20. As shown therein, the imaging system 20 includes an infrared based thermal imaging camera 22 that is communicably coupled to a computing means 24 such as a common PC or controller that includes application software to implement the imaging system. The controller 24 may be disposed outside the camera 22, as seen in FIGS. 1 and 2, or may be disposed inside the camera (FIG. 2 shown in dashed lines). An interface 26 to couple the PC with the camera 22, such as a digital frame grabber 26, may be disposed between the controller 24 and the camera 22. As generally illustrated in FIG. 1 and in detail in FIG. 2, the thermal imager 22 captures a thermal image of one or more recently created seals 28. The thermal image is then processed and evaluated by the pre-programmed controller 24 to determine whether the seal 28 is of acceptable quality. As illustrated in FIGS. 1 and 3, the imaging system 20 may be used to detect seal defects on a seal 28 created by adhering two or more sheets of plastic together that may be transported on a conveyor or other transport mechanism. However, as those of ordinary skill in the art would recognize, the imaging system 20 may be used to detect seal defects on a variety of seals, such as on form fills, containers, etc. whether moving or not. [0018]A variety of suppliers make thermal imagers that might be suitable for this application. One common type of infrared camera is based on microbolometer technology and has a typical spectral response range of 7 to 14 microns. Most of the packaging materials use thin plastics that have varying degrees of transmission in this region. The greater the transmission the more of the background the camera sees rather than the packaging material. Plastic has various regions which are substantially more opaque than others. There are many plastic formulations that will shift where the most opaque region is. To maximize the camera's sensitivity to the defects in the seals 28, the camera's spectral response should be tailored to the target material. There is a tradeoff in camera performance when the spectral range is reduced so it is best to make the spectral range as wide as possible. A good compromise for the microbolometer camera is a region of 7.5 to 8.2 microns. However, with other types of cameras a region centered near 3.4 microns may work as well. [0019]As illustrated in FIG. 2, the camera 22 includes a lens 30 operatively connected to a detector or detector array 32. The camera 22 may also include a spectral filter to closely match the emission characteristics of the seal 28 or target material. The lens 30 optically compresses and guides the thermal image of the seal 28 onto the detector or detector array 32. The typical array 32 has a video format of 320.times.240 pixels yielding 76800 measurement points or pixels, but other array designs could use other formats, including but not limited to, 640.times.480 and 160.times.120. The array 30 is operatively connected to a plurality of array electronics 34 that convert the information in each piece of the array 32 to an electronic signal. Continue reading... Full patent description for Method and apparatus for analyzing thermo-graphic images to detect defects in thermally sealed packaging Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Method and apparatus for analyzing thermo-graphic images to detect defects in thermally sealed packaging patent application. ###  How KEYWORD MONITOR works... a FREE service from FreshPatents1. Sign up (takes 30 seconds). 2. Fill in the keywords to be monitored. 3. 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